diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
index 6b8fe2835a3..89c840658f0 100644
--- a/libcpp/ChangeLog
+++ b/libcpp/ChangeLog
@@ -1,3 +1,8 @@
+2014-08-20  Marek Polacek  <polacek@redhat.com>
+
+	* include/cpplib.h (cpp_options): Use signed char.
+	* lex.c (_cpp_lex_direct): Don't warn in C++ mode.
+
 2014-08-19  Marek Polacek  <polacek@redhat.com>
 
 	* lex.c (_cpp_lex_direct): Fix a typo.
diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index b89ba200699..9f87ff8b514 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -467,7 +467,7 @@ struct cpp_options
   bool restore_pch_deps;
 
   /* True if warn about differences between C90 and C99.  */
-  char cpp_warn_c90_c99_compat;
+  signed char cpp_warn_c90_c99_compat;
 
   /* Dependency generation.  */
   struct
diff --git a/libcpp/lex.c b/libcpp/lex.c
index 827cfb0d75f..5366dad9e44 100644
--- a/libcpp/lex.c
+++ b/libcpp/lex.c
@@ -2338,6 +2338,7 @@ _cpp_lex_direct (cpp_reader *pfile)
 	    }
 	  /* Or if specifically desired via -Wc90-c99-compat.  */
 	  else if (CPP_OPTION (pfile, cpp_warn_c90_c99_compat) > 0
+		   && ! CPP_OPTION (pfile, cplusplus)
 		   && ! buffer->warned_cplusplus_comments)
 	    {
 	      cpp_error (pfile, CPP_DL_WARNING,